Discussion
When you resize different layer types, you get different results. Vector shape layers, such as text or shape layers, can be resized larger or smaller without loss of quality.
Smart Objects can also be resized larger or smaller without loss of quality, depending on the original file. If the original file is a vector graphic, the Smart Object can be resized without ever losing quality. If the original file is a GIF or similar, the Smart Object can be resized up to the size of the image dimensions, above which it will start to lose quality.
Raster layers or selections can only be resized smaller. Resizing them larger will usually result in loss of quality.

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